The Solar Impulse began its journey in May in California (Picture: AP/File)

A solar-powered plane is one leg away from crossing the US.

The giant Solar Impulse touched down early morning at Dulles International airport, near Washington DC, after 14 hours in the air.

Although the penultimate leg took longer in the air than by car, pilot and co-creator Bertrand Piccard said the trip had already proven the ‘reliability and potential of clean technologies’.

The single-seat Solar Impulse, which weighs about the same as a car, reaches speeds of around 40mph and cannot travel through clouds, began its journey in May in California, later flying over Arizona, Texas, Missouri and Ohio.

Andre Borschberg is due to fly the final leg to New York next month, while the Swiss team behind the plane also have an eye on a 2015 worldwide attempt.